UNITED NATIONS -LRB- CNN -RRB- -- Coca cultivation and cocaine production have decreased in Colombia but increased in Bolivia and Peru , the United Nations reported .

Workers help eradicate coca plantations in northwest Colombia in May .

Colombian cultivation was down 18 percent , and production decreased 28 percent in 2008 , the U.N. Office on Drugs and Crime said in a report issued Friday .

But cultivation increased 6 percent in Bolivia and 4.5 percent in Peru , the report said . Likewise , production went up 9 percent in Bolivia and 4.1 percent in Peru .

`` The increases for Bolivia and Peru show a trend in the wrong direction , '' said Antonio Maria Costa , executive director of the U.N. drug office .

Much of the decline in Colombia resulted from the manual eradication of 237 acres of coca , an increase of 44 percent over 2007 , and the spraying of another 328 acres with herbicide , the U.N. said .

The production level is at a 10-year-low , the report said , and the cultivation amount is down to 2004 to 2006 levels .

`` This is a remarkable achievement , '' Costa said in a release . `` It means that more coca bush was eradicated in Colombia than was grown in all of Bolivia and Peru . ''

The value of coca leaf in Colombia is decreasing , making it less attractive for farmers -- 20,000 fewer households grew coca in 2008 than in 2007 , a decrease of 26 percent .

The drug trade also is being disrupted , the report said .

In Colombia , the U.N. said , authorities seized 200 tons of cocaine in 2008 , a 57 percent increase in seizures over 2007 , the report said .

Peru reported an 86 percent increase in seizures of coca base and a 100 percent increase in the seizure of cocaine .

Bolivia , likewise , reported a 45 percent uptick in seizures of coca base and a 145 percent increase in the seizure of cocaine .

`` Cocaine supply is shrinking , as is demand in major markets of North America while cocaine use in Western Europe has stopped growing , '' Costa said . `` This may explain why prices are up , and purity is down . This may also explain why cartels are becoming so violent . ''

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Coca cultivation , cocaine production decrease in Colombia , U.N. report says

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But both on rise in Peru and Bolivia , report finds

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U.N. official : `` Increases for Bolivia and Peru show a trend in the wrong direction ''

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Production level is at a 10-year low , report says